Importing a space breaks Multiexcerpt Include but it works after you navigate through all excerpt pages
The Multiexcerpt app requires that an excerpt be visited by viewing the page it is on in order to create the index that includes need in order to find the excerpt.
For scenarios where a space is exported/imported or copied, or scenarios where a page tree is copied the indexes for the excerpts will not be built because the pages have not been visited yet.
Until the pages with the excerpts on them are visited the includes will not be able to find the excerpts.
Visit all new pages with excerpts on them after you copy/import a space or page tree.